package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import org.yaml.snakeyaml.events.Event;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    //TODO 缓存穿透
    public <R,ID> R queryWithPassThrough(           //函数逻辑
            String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit){
        //提前创建一个key值，将"cache:shop:"封装为一个常量，放在RedisConstants中
        String key =  keyPrefix + id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3.存在，直接返回
            return JSONUtil.toBean(json,type);
        }
        //缓存穿透，判断命中的是否是空值
        if (json != null){    //不等于null，也就是空字符串
            //返回错误信息
            return null;
        }
        //4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5.不存在，返回错误
        if (r == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            //返回错误信息
            return null;
        }
        //6.存在，写入redis   将shop转为一个Jsonstring类型存入redis
        this.set(key, r, time, unit);
        //7.返回
        return r;
    }


    //TODO 逻辑过期解决缓存击穿问题
    //TODO 创建线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(
            String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback, Long time, TimeUnit unit){
        //提前创建一个key值，将"cache:shop:"封装为一个常量，放在RedisConstants中
        String key =  keyPrefix + id;
        //1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(json)) {
            //3.不存在，直接返回空
            return null;
        }
        //TODO 4.命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data =(JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();

        //TODO 5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //TODO 5.1 未过期，直接返回店铺信息
            return r;
        }
        //TODO 5.2 已过期，需要缓存重建
        //TODO 6.缓存重建
        //TODO 6.1 获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        //TODO 6.2 判断是否获取锁成功
        if (isLock){
            //TODO 6.3 成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //重建缓存
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入Redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //TODO 6.4 返回过期的商铺信息
        return r;
    }

    //TODO 获取锁
    private boolean tryLock(String key){

        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //TODO 释放锁
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }
}
